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The patient is a 71 year old woman with end stage renal disease and acquired cystic kidney disease secondary to diabetes. Five years after renal transplant, surveillance ultrasonography revealed complex cysts in the native right kidney, up to 1.9 cm in greatest dimension. Renal MRI confirmed the presence of multiple complex cystic lesions in the bilateral native kidneys, including an enhancing nodule within one of the lesions, concerning for malignancy. Bilateral nephrectomy was performed.

Clear cell papillary renal cell carcinoma has distinctive histologic features, though sometimes showing significant morphologic overlap with clear cell carcinoma or papillary carcinoma. Architectural features include a mixture of cystic, solid tubular/ductular, and branched papillary architectural components, combined cytologically with variable amounts of clear cytoplasm (Am J Surg Pathol 2010;34:1608, Histopathology 2011;58:1064, Am J Surg Pathol 2006;30:141). Often, at least focal areas show alignment of the tumor cell nuclei away from the basement membrane, similar to secretory endometrium. Other features include a branched configuration of the ductular/tubular component and occasional calcification within the fibrous septa. Although the tumor is named for the combination of clear cell cytology and papillary architecture, large, extensively branched papillae are not the predominant component in many cases. Some cases may be predominantly cystic, mimicking multilocular cystic renal cell carcinoma. Most show low-grade nuclear features (Fuhrman grade 1 or 2).

A characteristic molecular-genetic abnormality has not yet been identified. Some studies have found low copy number gains of chromosome 7 or 17 in a minority of cases, similar to, although less frequent than, papillary carcinoma. In contrast to clear cell carcinoma, abnormalities of chromosome 3p and the VHL gene are absent, although expression of CA-IX, HIF-1α, and GLUT-1 has led to the hypothesis that there is upregulation of the HIF pathway by a non-VHL-dependent mechanism (Mod Pathol 2011;24:1207).

Prognosis in tumors reported thus far has been excellent, with no known metastases or aggressive behavior.